Might it be an idea to add the following rule, or something like it;
" The CT initiating a death game is the designated shooter."
basically meaning that the CT starting the death game with a group of Ts is the one who calls the shots about who lives and dies, and other CTs cannot shoot them.
Quite often I want to play a death game with some T's and then a random CT pops one in the head for assuming that guy lost, yet most of the time those CTs did not hear the rules properly, or falsely shoot the T =/